The lean startup methodology (popularized by Eric Ries in his book The Lean Startup) calls for startups to develop products iteratively—that is, to build a "minimum viable product" that will gauge demand and maximize the ways a business can learn from its customers while minimizing investment on the product itself. Customer feedback is then applied to quickly develop and launch the next version. The thinking is that by focusing on discovering customer needs rather than predicting them, companies won't waste significant resources building products that nobody wants. The concept of "lean," however, doesn't end there.